EG4 18kPV
For grid-tied homes that want whole-house backup and grid sell from one proven inverter. Compare against the FlexBOSS21 first, which costs less for more power.
Signature Solar $3,999.99 Shop Solar Kits $3,999.99$3,999.99
The EG4 18kPV is the better hybrid solar inverter overall, rated 4.3 to 4.2. The EG4 18kPV leads on value. The Fortress Power Envy True 12 wins on solar input. The EG4 18kPV costs $898.01 less ($3,999.99 vs $4,898).
Fortress Power Envy True 12
For grid-tied or off-grid homes that want one outdoor inverter to back up the whole house and export to the grid, with US-based support.
Current Connected $4,898 Wind & Sun $4,898$4,898
Prices were last checked October 23, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the EG4 18kPV for value ($333 per kW of continuous output vs $408 per kW of continuous output).
- Choose the Fortress Power Envy True 12 for solar input (21,000 W of panels, 600 V max, 3 MPPTs vs 18,000 W of panels, 600 V max, 3 MPPTs).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 120/240 V split-phase hybrid solar inverter; a clear win is highlighted. How we rank explains each one.
| Factor weight | EG4 18kPV | Fortress Power Envy True 12 |
|---|---|---|
| Overall rating | 4.3/5 | 4.2/5 |
| Value 30% | 73 $333 per kW of continuous output | 58 $408 per kW of continuous output |
| Solar input 20% | 75 18,000 W of panels, 600 V max, 3 MPPTs | 88 21,000 W of panels, 600 V max, 3 MPPTs |
| Efficiency 20% | 63 94% peak efficiency, 70 W idle | 63 94% peak efficiency, 70 W idle |
| Features 15% | 100 UL 1741 listed, Wi-Fi app, parallel stacking, grid sell-back, generator input, battery communication | 100 UL 1741 listed, Wi-Fi app, parallel stacking, grid sell-back, generator input, battery communication |
| Warranty 15% | 100 10-year warranty | 100 10-year warranty |
Independent measurements
EG4 18kPV
No independent test published yet.
Fortress Power Envy True 12
| Tested by | Efficiency | Idle draw | Conditions |
|---|---|---|---|
| The Solar Lab | - | 80 W | About 80 W idle measured off-grid on battery only. |
Specifications
| EG4 18kPV | Fortress Power Envy True 12 | |
|---|---|---|
| Output | ||
| Output voltage | 120/240 V split-phase | 120/240 V split-phase |
| Continuous output | 12,000 W | 12,000 W |
| Surge | 15,500 W | 20,000 W |
| Peak efficiency | 94% | 94% |
| CEC efficiency | 96.9% | 96.5% |
| Idle draw | 70 W | 70 W |
| Transfer time | 20 ms | 20 ms |
| Parallel units | Up to 10 units | Up to 10 units |
| Solar | ||
| Max PV power | 18,000 W | 21,000 W |
| Max PV voltage (Voc) | 600 V | 600 V |
| MPPT range | 140 to 500 V | 230 to 500 V |
| MPPT trackers | 3 | 3 |
| PV current per tracker | 25 A | 25 A |
| Runs without battery | Yes | Yes |
| Battery and grid | ||
| Battery voltage | 48 V | 48 V |
| Battery types | Lithium, lead-acid | Lithium, lead-acid |
| Max charge current | 250 A | 250 A |
| Battery communication | Yes | Yes |
| Grid sell-back | Yes | Yes |
| Generator input | Yes | Yes |
| UL 1741 | UL 1741 SB | UL 1741 SB |
| Build | ||
| App monitoring | Included | Included |
| Enclosure | NEMA 4X | IP65 (NEMA 4X) |
| Dimensions | 34.3 x 20.5 x 11.2 in | 34.2 x 20.5 x 11.2 in |
| Weight | 121 lb | 127 lb |
| Warranty | 10 years | 10 years |
| Released | 2023-05 | 2023-04 |